If 5 letters are to be placed in 5 -addressed envelopes, then the probability that at least one letter is…
If 5 letters are to be placed in 5 -addressed envelopes, then the probability that at least one letter is placed in the wrongly addressed envelope is
$\frac{1}{5}$
$\frac{1}{120}$
$\frac{4}{5}$
$\frac{119}{120}$
Solution
Since, total number of ways in which 5 letters are placed in 5 -addressed envelopes $=5!=120$
Now, the probability of all letters placed is correct placed
$=\frac{1}{120}$
So, P (at least one letters wrongly) $=$ $1-\frac{1}{120}=\frac{119}{120}$